Mexico
Republic Pattern 8 Reales 1840 Do-OMC AU53 NGC, KMPn59. Other than a test mark at 12:00 and some handling evidence in accordance with the assigned grade, a rather attractive specimen of this rare and mysterious pattern issue. The cataloguer considers it a proposal strike issued by a private minting company, namely the French firm Oeschger Mesdach & Co (standing for the "O. M. C." initials). The coin presents enough characteristics (particularly its edge) to assign a European origin to it and Kent Ponterio ("The Durango Mint Pattern 8 Reales of 1840", in NI Bulletin and http://numis.org/wp-content/uploads/2014/04/Durango8.pdf) presented logical arguments strongly suggesting ties to said firm.
Estimate: 1500-2000 USD